Method of Preparing Positive Electrode Active Material for Lithium Secondary Battery and Positive Electrode Active Material Prepared Thereby

Abstract

A method of preparing a positive electrode active material for a lithium secondary battery which includes: (1) mixing a lithium composite transition metal oxide in a form of a single particle or pseudo-single particle with a cobalt-containing raw material and performing a heat treatment to form a cobalt coating layer on a surface of the lithium composite transition metal oxide; and (2) mixing the lithium composite transition metal oxide having the cobalt coating layer formed thereon with a boron-containing raw material and performing a heat treatment to form a boron coating layer on the cobalt coating layer. A positive electrode active material for a lithium secondary battery which is prepared thereby, is also provided.

1 . A method of preparing a positive electrode active material for a lithium secondary battery, comprising:
 (1) mixing a lithium composite transition metal oxide in the form of a single particle or a pseudo-single particle with a cobalt-containing raw material and performing a first heat treatment to form a cobalt coating layer on a surface of the lithium composite transition metal oxide; and   (2) mixing the lithium composite transition metal oxide having the cobalt coating layer formed thereon with a boron-containing raw material and performing a second heat treatment to form a boron coating layer on the cobalt coating layer.   
     
     
         2 . The method of  claim 1 , wherein the single particle is a particle composed of one primary particle, and
 the pseudo-single particle is a particle composed of a secondary particle in which 30 or less primary particles are aggregated.   
     
     
         3 . The method of  claim 1 , wherein the cobalt-containing raw material is mixed in an amount of 1 wt % to 5 wt % based on a total amount of the lithium composite transition metal oxide. 
     
     
         4 . The method of  claim 1 , wherein the boron-containing raw material is mixed in an amount of 0.03 wt % to 0.08 wt % based on a total amount of the lithium composite transition metal oxide having the cobalt coating layer formed thereon. 
     
     
         5 . The method of  claim 1 , wherein the first heat treatment is performed at 600° C. to 800° C. 
     
     
         6 . The method of  claim 1 , wherein the second heat treatment is performed at 250° C. to 400° C. 
     
     
         7 . The method of  claim 1 , wherein the lithium composite transition metal oxide is represented by Formula 1: 
       
         
           
           
               
               
           
         
         in Formula 1, 
         1.0≤a≤1.5, 0≤x≤0.2, 0≤y≤0.2, 0≤w≤0.1, and 0≤x+y≤0.4, 
         M1 is at least one selected from the group consisting of Mn and Al, and 
         M2 is at least one selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo. 
       
     
     
         8 . The method of claim  47 , wherein x, y, and w of Formula 1 satisfy 0.025≤x≤0.15, 0.025≤y≤0.15, 0≤w≤0.05, and 0.05≤x+y≤0.2, respectively. 
     
     
         9 . A positive electrode active material for a lithium secondary battery, comprising:
 a lithium composite transition metal oxide in the form of a single particle or a pseudo-single particle,   a cobalt coating layer formed on the lithium composite transition metal oxide, and   a boron coating layer formed on the cobalt coating layer.   
     
     
         10 . The positive electrode active material of  claim 9 , wherein the single particle is a particle composed of one primary particle, and
 the pseudo-single particle is a particle composed of a secondary particle in which 30 or less primary particles are aggregated.   
     
     
         11 . The positive electrode active material of  claim 10 , wherein the primary particle has an average particle diameter of 1 μm to 5 μm. 
     
     
         12 . The positive electrode active material of  claim 9 , wherein the positive electrode active material has an average particle diameter of 3 μm to 10 μm. 
     
     
         13 . The positive electrode active material of  claim 9 , wherein the lithium composite transition metal oxide is represented by Formula 1: 
       
         
           
           
               
               
           
         
         wherein, in Formula 1, 1.0≤a≤1.5, 0≤x≤0.2, 0≤y≤0.2, 0≤w≤0.1, and 0<x+y≤0.4, 
         M1 is at least one selected from the group consisting of Mn and Al, and 
         M2 is at least one selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo. 
       
     
     
         14 . A positive electrode comprising a positive electrode active material layer which includes the positive electrode active material of  claim 9 . 
     
     
         15 . A lithium secondary battery comprising the positive electrode of  claim 14 . 
     
     
         16 . A lithium secondary battery comprising the positive electrode of  claim 14  and a negative electrode.